The device is intended to provide a constant dynamic extensor moment to the pelvis. Its purpose is twofold: 1) to prevent the occurence of hip contractions and the compensatory abnormalities such as excessive lordosis and knee flexion contractions that predictably develop in the L 3,4 and 5 level Myelomeningocele child. 2) To improve gait and make other activities easier, by making the action of the extensor moment to the pelvis reciprocal. The key to prevention is to apply the orthotic device at a very early age (possibly as early as the 12th month) before the hips become contracted. With this device, a low-magnitude extensor moment is acting on the pelvis whenever the child is standng at ease. Thus providing a constant 'stretch' mechanism to innervated muscles that cross the hip joints and thereby preserving their normal rest lengths when in an upright posture. The magnitude of the extensor moment to the pelvis is automatically increased as innervated muscles are called upon to produce motion, e.g., hip flexion, knee extension or trunk forward flexion. The increased extensor moment stabilizes the pelvis by acting as an opposition force to prevent out-of-sequence motion of the pelvis. The magnitude of the extensor moment provided by the system is also sufficient to prevent involuntary forward rotation of the trunk about the hip joints (sway in an anterior direction), when standing. We feel that involuntary sway is the trigger that causes excessive lordosis -the only anatomic means available for AP balance when the trunk's extensors are paralyzed. Elastic is used to generate the extensor moment to the pelvis. Reciprocation is achieved by transferring the elastic force from side-to-side, via the moveable pelvic portion. To summarize: The power of active muscles is used in such a manner as to produce an opposition force to check and/or enhance their function.